In a campaign, go to the token search tab, and then click the little star to the right to bring up 'Your Art Library'.
Once there, you can choose any file you've uploaded and assign tags to them. Then, when searching for tokens / maps, etc, you can just type in a tag, and you'll get everything that matches. Each upload is automatically assigned a tag based on its filename.
For example: all of my tokens get a 'token' tag. All tokens with a melee weapon also get a 'melee' tag. Likewise, I have tags for orientation ('top-down' and 'portrait'), armor types, animals, troop cards, character sheet images, colors, etc. Basically, anything that you'd want to sort your images on can be added as a tag.
Also, note: while in your library, you can select multiple images at once, and then apply tags to all of them using the little pop-up that appears.
Hope that helps a little!
